Exhaust systems - What you need to Know

Was that the part where the exhaust is tuned to assist in the filling and scavenging of the cylinders?

Originally Posted by Cuore_Sportivo_155

was just about to add a brief introduction to harmonics...

Go on then - not just the teaser, but give us your opinion please. I want to reduce my noise in the 2400 to 2800 rpm range on my V6.

Originally Posted by fantom alfa

Go on then - not just the teaser, but give us your opinion please. I want to reduce my noise in the 2400 to 2800 rpm range on my V6.

unfortunatly it doesn't work like that

Originally Posted by fantom alfa

Go on then - not just the teaser, but give us your opinion please. I want to reduce my noise in the 2400 to 2800 rpm range on my V6.

Put a potato up the exhaust.

Originally Posted by 156_TSpark_Boy

Ok so when a manifold is not a single unit like a 4branch 4-2-1 or 4-1 some manufactors use a cast iron construction manifold which can come in either two or three parts.

The first part directly bolts to the head and and is basically a 90' angle the directs all 4exits from the head in the next part which normally 'L' shaped which joins the top half of the manifold which is connected to the head the other end joins either the begin of the exhaust system of the cat.

As you can see from the attached image the above is a cast iron unit which just pipes joining pipes which is bad for gas flow, where as the stainless steel tubular (as they are otherwise called) has pipes joining at ruffly the same points which aids gas flow.



Manifold designs are alot more complicated than just getting all the pipes from the head to join with the exhaust system. Big power gains can be seen from a change of manifold.

The top example doesn't look too like a cast iron jobbie to me, if you don't mind my saying so! There seem to be an awful lot of welds on it!!

I googled anumber of words including 'Cast Iron Manifold' but that was the best image that showed a older manifold compared to a more upto date 4branch.

it is welded though, not cast...

the reson it's hard to find a direct comparison between a tubed header and a casted manifold is the size.. cast iron pieces are usually small, aftermarket headers usually replace the manifold and downpipe together

But the Vovo's in the earlier post is a good example of a cast iron manifold.

Alfa's 4 cyl 2.0 t/c unit is pretty good as cast iron units go and replacing it with one of Mr. Conrero's spaghetti type only used to produce another 3-4bhp. A decent free flow system will give that and should cost less.

I'll do a piece on Stage 1 tuning if anybody's interested.

Very interesting stuff.

Yes please - would love some info there.

you can't really discuss header design/improvement and ignore exhaust cam timing though...

In other words, header optimisation relies on engine cc's, exhaust cam duration, and what you are optimising for.

It also means that if you fit another set of cams your header is by definition not optimal...

I think its important to understand the basics that lead onto the more indepth tuning.

The first post still sands as a ruff guide and yes there is of course alot of other advice interms of tuning set around the exhaust system but what you have to think about is how far do you go before you start talking about stage 1 tuning rather than simple bolt mods.

Please bear in mind there are alot of people that just have simple exhaust system questions like:

Will a back box improve my cars performance
What is a 4branch manifold

great thread keep up the good work tspark and others. my head hurts and im getting eye strain from staring at the screen in begogglement. thanks again

Originally Posted by 156_TSpark_Boy

The first post still sands as a ruff guide and yes there is of course alot of other advice interms of tuning set around the exhaust system but what you have to think about is how far do you go before you start talking about stage 1 tuning rather than simple bolt mods

cams and a 'pipe are more than stage 1 !! But i never did like this stage 1,2,3 etc mallarky anyway...

If your going to do it, do it right first time, properly!

I respect the thread, good on you 156_TSpark_Boy !

I aggree for those who want to know more than just backbox's etc, then we should start a new thread for "in depth" performance tuning...
because indeed, no 2 engines are the same (even if they where 1 & 2 off the production line ) and knowing the basics of how to optimise engine pottential via harmonic tuning via exhaust, in conjunction with cams etc (yes they all live in each others pockets, you can't do one and not the other and expect a healthy power gain)

yes or no

yes... you could call it "exhaust systems-what you need to know 2"



IMO when you're going to the expense of changing the headers or cams, you should know this stuff or your money is largely wasted... in this case it's not one size fits all engines...

An enjoyable read!

RE custom exhausts, do they actually sound any good? I have found a company that can make a ss exhaust for 250 which IMO is a very good price. My concern is that it may not sound as good as the OEM one... Any views/ideas?

Cheers

Originally Posted by alfaspence

cams and a 'pipe are more than stage 1 !! But i never did like this stage 1,2,3 etc mallarky anyway...

If your going to do it, do it right first time, properly!

I respect the thread, good on you 156_TSpark_Boy !

I aggree for those who want to know more than just backbox's etc, then we should start a new thread for "in depth" performance tuning...
because indeed, no 2 engines are the same (even if they where 1 & 2 off the production line ) and knowing the basics of how to optimise engine pottential via harmonic tuning via exhaust, in conjunction with cams etc (yes they all live in each others pockets, you can't do one and not the other and expect a healthy power gain)

yes or no

two thumbs up from me, its important for people to know why and what effect engine performance both in standard layout and with tuning items like wild cams, ported and gas flowed heads etc etc

Originally Posted by ar 145

An enjoyable read!

RE custom exhausts, do they actually sound any good? I have found a company that can make a ss exhaust for 250 which IMO is a very good price. My concern is that it may not sound as good as the OEM one... Any views/ideas?

Cheers

that is a good price... be warned tho, some cheaper systems or "mufflers" that get used allow a very undesirable "rasp" (unless you like that sort of thing)

For that price, in stainless, it WILL be loud! 115 db + when on song... be sure thats what you want first...

perhaps we could call the thread

serious performance tuning, what you need to know...

As cams are a subject of their own, but are tied with exhausts, flowed heads, intakes etc

do you want to kick it off 156_TSpark_Boy as your thread has been so successful?

Be warned, this could get technical

Originally Posted by alfaspence

perhaps we could call the thread

serious performance tuning, what you need to know...

As cams are a subject of their own, but are tied with exhausts, flowed heads, intakes etc

do you want to kick it off 156_TSpark_Boy as your thread has been so successful?

Be warned, this could get technical

Ok I can start a slightly more tech quide to 'after breathing mods' but I cant say how far my know how will stretch

Originally Posted by 156_TSpark_Boy

Ok I can start a slightly more tech quide to 'after breathing mods' but I cant say how far my know how will stretch

we'll see dude, if i don't know off the top of my head, i have dozens of books ranging from blueprinting to 2 stroke performance tuning, also know a few pro's who have been in the game a lot lot longer than me